This invention relates to a polygonal packaging sleeve, more specifically to spiral packaging sleeves of layers of paper, synthetic fabrics or similar material, arranged one above the other and glued to each other, and to methods and devices for producing same.
Polygonal packaging sleeves are well known for space saving is an empty and full state, as opposed to the commonly used round packaging sleeves. However, transportation and storing of these sleeves before loading is so bulky that production thereof is only profitable when a small area is serviced, so that production of bigger quantities is limited. On the other hand, wrapped sleeves, as compared to folding cartons, have a substantially higher strength and superior rigidity, because they are made of individual layers of paper which are wrapped around. They can, therefore, not only be used as bigger containers, such as for powdered laundry detergent, but also for heavy machine parts and in sizes up to a few meters. The folded cartons commonly used break or tear easily at their glued or folded edges.
The commonly known packaging sleeves are wound from a plurality of strips of previously glued material. The strips are helically wound around a stationary spindle, whereby each strip is staggered laterally in the longitudinal direction of the sleeve. In order to produce such a multiplestage sleeve, a so-called spiral package-sleeve-machine is used, whereby the individual strips are pulled off from rolls. Before winding the wrapping strips around the spindle, they are glued; i.e. they are pulled on both sides through a tub of glue, by a dipping process, or on one side by a single glueing process. They are then carried over a roller which applies glue. The wall thickness of the spiral sleeves manufactured in this manner results from the number of the strips wrapped over each other and from the volume of the strip material.
The sleeve production takes place by the means of an endless belt which is rotated by two revolving heads. The belt forms a loop around the glued strips which are wrapped around the spindle and, by revolving, effects a pulling out of the wrapping material from the delivery rolls to the spindle, the tightening of the glued wrapping material against each other in order to glue it together, and the horizontal pushing off of the endless round sleeve which has been formed in this manner. The severing of the sleeve, in the desired places, takes place in such a manner than the sleeve runs against a buffer (plate) which is connected by means of a rod to a circular saw. At first the sleeve runs past the saw which is in resting position. Only when the sleeve is bearing on the buffer is the saw advanced horizontally and guided over a cam into the wall of the sleeve. The cutting process is finished as soon as the sleeve has rotated around its axis. According to another method of manufacturing round sleeves by cross wrapping or parallel wrapping, the paper web is pulled off a paper roller. Both paper edges can be buffed by a buffing device for the purpose of later glueing them to the sleeve on the inside and on the outside. Subsequently, glue is put on one side of the paper web, which is constantly pulled off and it is separated by a cross-cutting knife. The now loose paper web, which in its length is the sleeve length to be wrapped, in guided on one side onto a split spindle. The spindle starts to rotate after the paper web has been inserted and thereby wraps the paper laterally to the paper web but in the direction of the fiber of the paper. The desired thickness of the sleeve wall determines the width of the paper web and the thickness of the paper in this method of parallel wrapping. After the wrapping process is completed, the parallel sleeve formed in this manner is pushed off the spindle which is now in resting position to accept the next paper web, by means of a transfer conveyor.
A means for producing spirally wrapped sleeves with polygonal cross-sections is already known. On the spiral sleeve wrapping machine, a rotatable polygonal spindle is used instead of the stationary round wrapping spindle. On this rotatable polygonal spindle, just as in the case of producing a round sleeve, the preglued wrapping material is applied and is manufactured with the endless belt, as already described. In order that the sleeve can glide over the polygonal spindle, elongated horizontal slide bars are mounted on to the corners of the spindle, which bars decrease the contact area. The sliding areas of the bars must of course be well lubricated so that the horizontal movement of the sleeve is possible.
Economical production with high speed is not possible on a rotating polygonal spindle because the sliding areas decrease tge conveyability of the sleeve very much. Therefore, a constant bunching-up of the sleeve wall to the wrapping belt occurs.
Moreover, the belt in the case of a polygonal spindle moves constantly towards the saw and back again. This effect, also called pumping, results in the fact that the sleeves can only be produced with low speed and are only shaped polygonally but are not foldable.
Since the previously-mentioned manufacture of polygonal sleeves is disadvantageous, West German Pat. No. 1 943 097 describes another method for the continuous manufacture of spirally wrapped sleeves with polygonal cross section. This method of manufacturing is such that on a stationary spindle with a circular cross-section a round sleeve is produced, according to a known, already described method. The cylindrical sleeve so produced ends, when 50-100 cm in length, into a first rotary head. The sleeve is guided through rolls in this rotary head and is shaped by impressing it onto a rotary spindle with a polygonal cross section. Thereafter, further strips are wrapped onto the polygonal sleeve in order to give the sleeve the desired wall thickness. Subsequently, the sleeve, which has its wall thickness increased by further glued-on strips, is guided between the rolls of a second rotary head until finally the completed sleeve can be guided to the separation device. The sleeve manufactured in this manner requires an additional, expensive device with its own motor which has to run in synchronism with the wrapping sleeve machine, since, in this method of manufacturing, the sleeve has to be constantly pushed over a long, polygonal spindle and through two rotary heads with contact pressure, whereby additional strips still have to be applied, a constant friction on the spindle with polygonal cross section takes place, which also prevents economic manufacture.
According to such a manufacturing method, also known from French Pat. No. 1 119 280, packaging sleeves with polygonal cross section are known. However, various considerable disadvantages exist in the manufacture of these. The friction force which results from the passing over to the polygonal spindle is so considerable, that only a small manufacturing output can be realized with this method and furthermore, only wrapped sleeves limited to smaller wall thicknesses can be produced. In order to keep the friction on the polygonal spindle at a minimum, the edges of the spindle have to be kept comparatively sharp-edged. In addition, when employing this known method, the wrapped tube is visibly considerably distorted by pushing on to the polygonal spindle. It should here be taken into consideration that the wrapped sleeve has a deformable softened characteristic because of the glue.
Because of these influences, the sleeves manufactured in this known manner are comparably limited by size of their rounded-off edges.
Even when, as described in the cited U.S. Pat. No. 2,709,400, the formation of a polygonal cross section takes place through a roll which is forced against a roundly-wrapped sleeve from the outside, whereby comparatively sharply-edged sleeve cross-sections result. Specifically, this method is also mechanically not economical, i.e., primarily because the total roll-deformation device which is arranged outside the wrapped sleeve, has to rotate with a high wrapping speed, so that a considerable limitation of the wrapping performance exists.
It is an object of this invention to provide a polygonal packaging sleeve, the manufacture of which is considerably simplified and inexpensive and which can be done with little consumption of energy, so that its walls remain in this process smooth and without wrinkling along its longitudinal edges, whereby polygonal packaging sleeves can be manufactured not only cheaper in bigger manufacturing units, i.e. favorably priced, but also additionally will be economical in space when transported and stored in an empty state.